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Groups > linux.kernel > #1458289 > unrolled thread

[PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries

Started byBaoquan He <bhe@redhat.com>
First post2016-08-09 01:10 +0200
Last post2016-08-11 16:30 +0200
Articles 5 — 2 participants

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  [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries Baoquan He <bhe@redhat.com> - 2016-08-09 01:10 +0200
    Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle  apic/x2apic entries Ingo Molnar <mingo@kernel.org> - 2016-08-10 21:00 +0200
      Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle  apic/x2apic entries Baoquan He <bhe@redhat.com> - 2016-08-10 21:10 +0200
        Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle  apic/x2apic entries Ingo Molnar <mingo@kernel.org> - 2016-08-11 10:50 +0200
          Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle  apic/x2apic entries Baoquan He <bhe@redhat.com> - 2016-08-11 16:30 +0200

#1458289 — [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries

FromBaoquan He <bhe@redhat.com>
Date2016-08-09 01:10 +0200
Subject[PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries
Message-ID<s41Qd-7Ui-9@gated-at.bofh.it>
It won't impact the result, we still should fix the code bug.

Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-pm@vger.kernel.org
---
 arch/x86/kernel/acpi/boot.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 90d84c3..2b25d3f 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1031,8 +1031,8 @@ static int __init acpi_parse_madt_lapic_entries(void)
 			return ret;
 		}
 
-		x2count = madt_proc[0].count;
-		count = madt_proc[1].count;
+		count = madt_proc[0].count;
+		x2count = madt_proc[1].count;
 	}
 	if (!count && !x2count) {
 		printk(KERN_ERR PREFIX "No LAPIC entries present\n");
-- 
2.5.5

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#1459547 — Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries

FromIngo Molnar <mingo@kernel.org>
Date2016-08-10 21:00 +0200
SubjectRe: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries
Message-ID<s4GTp-n4-55@gated-at.bofh.it>
In reply to#1458289
* Baoquan He <bhe@redhat.com> wrote:

> It won't impact the result, we still should fix the code bug.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: linux-pm@vger.kernel.org
> ---
>  arch/x86/kernel/acpi/boot.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index 90d84c3..2b25d3f 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -1031,8 +1031,8 @@ static int __init acpi_parse_madt_lapic_entries(void)
>  			return ret;
>  		}
>  
> -		x2count = madt_proc[0].count;
> -		count = madt_proc[1].count;
> +		count = madt_proc[0].count;
> +		x2count = madt_proc[1].count;
>  	}
>  	if (!count && !x2count) {
>  		printk(KERN_ERR PREFIX "No LAPIC entries present\n");

Why does this bug have no effect?

Thanks,

	Ingo

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#1459603 — Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries

FromBaoquan He <bhe@redhat.com>
Date2016-08-10 21:10 +0200
SubjectRe: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries
Message-ID<s4H36-I0-89@gated-at.bofh.it>
In reply to#1459547
On 08/10/16 at 02:53pm, Ingo Molnar wrote:
> 
> * Baoquan He <bhe@redhat.com> wrote:
> 
> > It won't impact the result, we still should fix the code bug.
> > 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > Cc: Len Brown <len.brown@intel.com>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: x86@kernel.org
> > Cc: linux-pm@vger.kernel.org
> > ---
> >  arch/x86/kernel/acpi/boot.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> > index 90d84c3..2b25d3f 100644
> > --- a/arch/x86/kernel/acpi/boot.c
> > +++ b/arch/x86/kernel/acpi/boot.c
> > @@ -1031,8 +1031,8 @@ static int __init acpi_parse_madt_lapic_entries(void)
> >  			return ret;
> >  		}
> >  
> > -		x2count = madt_proc[0].count;
> > -		count = madt_proc[1].count;
> > +		count = madt_proc[0].count;
> > +		x2count = madt_proc[1].count;
> >  	}
> >  	if (!count && !x2count) {
          ~~~~~~~~~~~~~~~~~~~~~
I mean here the value checking won't be impacted by the wrong
assignment.

> >  		printk(KERN_ERR PREFIX "No LAPIC entries present\n");
> 
> Why does this bug have no effect?
> 
> Thanks,
> 
> 	Ingo

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#1460280 — Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries

FromIngo Molnar <mingo@kernel.org>
Date2016-08-11 10:50 +0200
SubjectRe: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries
Message-ID<s4TQC-1tP-41@gated-at.bofh.it>
In reply to#1459603
* Baoquan He <bhe@redhat.com> wrote:

> On 08/10/16 at 02:53pm, Ingo Molnar wrote:
> > 
> > * Baoquan He <bhe@redhat.com> wrote:
> > 
> > > It won't impact the result, we still should fix the code bug.
> > > 
> > > Signed-off-by: Baoquan He <bhe@redhat.com>
> > > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > > Cc: Len Brown <len.brown@intel.com>
> > > Cc: Pavel Machek <pavel@ucw.cz>
> > > Cc: Thomas Gleixner <tglx@linutronix.de>
> > > Cc: Ingo Molnar <mingo@redhat.com>
> > > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > > Cc: x86@kernel.org
> > > Cc: linux-pm@vger.kernel.org
> > > ---
> > >  arch/x86/kernel/acpi/boot.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> > > index 90d84c3..2b25d3f 100644
> > > --- a/arch/x86/kernel/acpi/boot.c
> > > +++ b/arch/x86/kernel/acpi/boot.c
> > > @@ -1031,8 +1031,8 @@ static int __init acpi_parse_madt_lapic_entries(void)
> > >  			return ret;
> > >  		}
> > >  
> > > -		x2count = madt_proc[0].count;
> > > -		count = madt_proc[1].count;
> > > +		count = madt_proc[0].count;
> > > +		x2count = madt_proc[1].count;
> > >  	}
> > >  	if (!count && !x2count) {
>           ~~~~~~~~~~~~~~~~~~~~~
> I mean here the value checking won't be impacted by the wrong
> assignment.

Indeed!

Mind putting that into the changelog? Something like:

"By pure accident the bug makes no functional difference, because the only 
 expression where we are using these values is (!count && !x2count), in which
 the variables are interchangeable, but it makes sense to fix the bug 
 nevertheless."

Thanks,

	Ingo

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#1460569 — Re: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries

FromBaoquan He <bhe@redhat.com>
Date2016-08-11 16:30 +0200
SubjectRe: [PATCH 2/2] x86, ACPI: Fix the wrong assignment when Handle apic/x2apic entries
Message-ID<s4Z9E-4XM-1@gated-at.bofh.it>
In reply to#1460280
On 08/11/16 at 10:46am, Ingo Molnar wrote:
> > > > -		count = madt_proc[1].count;
> > > > +		count = madt_proc[0].count;
> > > > +		x2count = madt_proc[1].count;
> > > >  	}
> > > >  	if (!count && !x2count) {
> >           ~~~~~~~~~~~~~~~~~~~~~
> > I mean here the value checking won't be impacted by the wrong
> > assignment.
> 
> Indeed!
> 
> Mind putting that into the changelog? Something like:
> 
> "By pure accident the bug makes no functional difference, because the only 
>  expression where we are using these values is (!count && !x2count), in which
>  the variables are interchangeable, but it makes sense to fix the bug 
>  nevertheless."

Sure, this is much clearer. Will use this and repost. Thanks a lot, will
try to do each post using patch log like this.

Thanks
Baoquan

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